Japan Post claimed at a court hearing Thursday that its tieup with convenience store operator Lawson Inc. in the parcel delivery business does not constitute dumping in violation of the Antimonopoly Law.

The government-backed corporation demanded at the first hearing in a suit filed by Yamato Transport Co. that the Tokyo District Court reject the courier's demand for a halt to the alliance between Japan Post and Lawson.

Yamato filed the lawsuit against Japan Post in late September, maintaining that its parcel delivery business expansion through Lawson's nationwide network would be unfair under the Antimonopoly Law as long as it receives preferential treatment in taxation and other areas.

At the hearing, Japan Post said in a statement that Yamato's claim is "intended to restrict the entry of competitors into the parcel delivery market and to maintain its overwhelming share there."

Yamato said in defense that the public corporation overwhelms the courier in terms of combined assets and sales.

"Which of the two is grand champion?" a lawyer for Yamato asked. Yamato then requested that presiding Judge Seiichiro Nishioka swiftly conclude the case.

Japan Post announced its tieup with Lawson in August, angering Yamato Transport, which had an exclusive partnership contract with the convenience store chain operator.

Lawson has offered to renew the contract with Yamato Transport when it expires Nov. 19, so that it can handle both Japan Post and Yamato Transport parcels.

Yamato Transport rejected the offer in August and accused Japan Post of "launching offensives" against private companies.